The present invention relates to a device for exerting thrust on the vertical surface of a door to open it by staving said door in. The present invention also relates to a method of exerting a thrust, preferably of at least 50 kN [kilonewton], on a door or any other vertical planar surface from external jacking points.
More particularly, the invention relates to a device for forcibly opening as rapidly as possible, without impact and in silence, any type of door in a dwelling, or in industrial or other premises.
Such devices are primarily intended for use either by emergency services such as fire departments or rescue services, or by specialized police units.
FR 2 825 354 discloses devices of that type, which comprise:                an actuator, preferably hydraulic, an intermediate soleplate and an upper jacking bar;        said actuator comprising a movable rod with one end fixed in hinged manner, preferably detachably, to said intermediate soleplate; and said upper jacking bar being fixed in hinged manner, again preferably detachably, by one of its ends to said intermediate soleplate.        
The hinging of the end of the movable rod of said actuator on said intermediate soleplate means that it can be inclined, preferably at 20° to 35° to the vertical, in order to be able to exert thrust, preferably of at least 50 kN, on said intermediate soleplate when said intermediate soleplate is pressed against said door or said vertical planar surface and when said actuator presses against a lower external jacking point, preferably on the ground.
Similarly, the hinging of said upper jacking bar on said intermediate soleplate means that said bar can be disposed substantially vertically so that its free end can be applied directly to an upper external jacking point, preferably constituted by the frame of said door, as can be seen in FIG. 1A, or a ceiling, or a horizontal flat surface located above said vertical planar surface. The term “free end” as used here means the end of said bar that is not fixed to said intermediate soleplate.
That device is ideally suited to opening doors that open by pushing on the side on which the door opening device is located, i.e. doors termed “push” doors that open into the inside of a room that is to be entered from its outside.
In practice, the device functions on push doors by pressing against three points, namely:                the ground;        on the door; and on the upper portion or lintel of the frame retaining the door and against which the door abuts.        
The upper end of the upper jacking bar abuts below and against the portion of the lintel of the door frame that projects relative to the vertical plane of the surface of the door and against which the upper end of the door abuts. That portion of the lintel, which is lower than the upper end of the door, retains the door in its frame when the door is closed by pulling it.
In contrast “pull” type doors, i.e. doors that open by being pulled outwards from the room that is to be entered from the outside, do not have the same door frame configuration. On the side outside the room, there is no upper bearing portion projecting from the door frame against which the upper end of the upper jacking bar could press.
Furthermore, the inventors have discovered that this absence of a door frame retainer and abutment on the outside of the door, for pull doors, gives rise to a second problem in the operation of the door forcing device described above. When the upper bar of the device inclines when the door starts to stave in at the intermediate soleplate, namely substantially at mid-height, the upper end of the door is not retained, and so the central thrust at the intermediate soleplate is less effective in staving in the door, thus slowing down opening of the door.